Développement d'une base de données thermodynamique de type ingénierie pour l'élaboration des alliages Al-Si-Fe-Mn-(Cr-Ni-V)

RÉSUMÉ: Les alliages à base d’aluminium sont les alliages non ferreux les plus utilisés dans le monde et connaissent une croissance importante soulignée par une augmentation de 6% de la production mondiale de ce métal en 2017 [1]. La production de ce métal se fait à partir de la bauxite, un minerai traité par les procédés Bayer et Hall-Héroult afin d’en extraire de l’aluminium pur. Cependant, il faut noter que le procédé Bayer qui consiste à séparer l’alumine de la bauxite, ainsi que le procédé Hall-Héroult qui repose sur plusieurs réactions d’électrolyse, ne purifient pas totalement l’aluminium final et y laissent des traces des divers éléments contenus dans le minerai primaire et dans les électrodes respectivement. L’aluminium primaire produit n’est donc pas pur et contient des impuretés telles que le silicium, le fer, le chrome, le nickel et le vanadium issues des procédés d’extraction. À cela peuvent s’ajouter des éléments d’addition volontairement introduits pour atteindre des caractéristiques thermodynamiques plus spécifiques tels que le silicium, le fer et le manganèse. Ces éléments peuvent jouer un rôle important sur la thermodynamique des alliages en favorisant notamment la formation de certaines phases intermétalliques fragilisantes ou de défauts de surface macroscopiques tels que les Fir-Tree-Zones par exemple.ABSTRACT:----------Aluminium-based alloys are the most widely used non-ferrous alloys in the world and are experiencing significant growth, highlighted by a 6% increase in world production of this metal in 2017 [1]. This metal is produced from bauxite, an ore processed by the Bayer and Hall-Héroult processes to produce pure aluminum. However, it should be noted that the Bayer process, which consists in separating alumina from bauxite, as well as the Hall-Héroult process, which is based on several electrolysis reactions, does not completely purify the final aluminum and leaves traces of the various elements contained in the primary ore and electrodes respectively. The primary aluminium produced is therefore not pure and contains impurities such as silicon, iron, chromium, nickel and vanadium from the extraction processes. To this can be added addition elements voluntarily introduced to achieve more specific thermodynamic characteristics such as silicon, iron and manganese. These elements can play an important role in the thermodynamics of alloys by promoting the formation of certain weakening intermetallic phases or macroscopic surface defects such as Fir-Tree-Zone for example

Spectral effects and enhancement quantification in healthy human saliva with surface-enhanced Raman spectroscopy using silver nanopillar substrates

ABSTRACT: Objectives Raman spectroscopy as a diagnostic tool for biofluid applications is limited by low inelastic scattering contributions compared to the fluorescence background from biomolecules. Surface-enhanced Raman spectroscopy (SERS) can increase Raman scattering signals, thereby offering the potential to reduce imaging times. We aimed to evaluate the enhancement related to the plasmonic effect and quantify the improvements in terms of spectral quality associated with SERS measurements in human saliva. Methods Dried human saliva was characterized using spontaneous Raman spectroscopy and SERS. A fabrication protocol was implemented leading to the production of silver (Ag) nanopillar substrates by glancing angle deposition. Two different imaging systems were used to interrogate saliva from 161 healthy donors: a custom single-point macroscopic system and a Raman micro-spectroscopy instrument. Quantitative metrics were established to compare spontaneous RS and SERS measurements: the Raman spectroscopy quality factor (QF), the photonic count rate (PR), the signal-to-background ratio (SBR). Results SERS measurements acquired with an excitation energy four times smaller than with spontaneous RS resulted in improved QF, PR values an order of magnitude larger and a SBR twice as large. The SERS enhancement reached 100×, depending on which Raman bands were considered. Conclusions Single-point measurement of dried saliva with silver nanopillars substrates led to reproducible SERS measurements, paving the way to real-time tools of diagnosis in human biofluids

Saliva-based detection of COVID-19 infection in a real-world setting using reagent-free Raman spectroscopy and machine learning

ABSTRACT: SIGNIFICANCE: The primary method of COVID-19 detection is reverse transcription polymerase chain reaction (RT-PCR) testing. PCR test sensitivity may decrease as more variants of concern arise and reagents may become less specific to the virus. AIM: We aimed to develop a reagent-free way to detect COVID-19 in a real-world setting with minimal constraints on sample acquisition. The machine learning (ML) models involved could be frequently updated to include spectral information about variants without needing to develop new reagents. APPROACH: We present a workflow for collecting, preparing, and imaging dried saliva supernatant droplets using a non-invasive, label-free technique-Raman spectroscopy-to detect changes in the molecular profile of saliva associated with COVID-19 infection. RESULTS: We used an innovative multiple instance learning-based ML approach and droplet segmentation to analyze droplets. Amongst all confounding factors, we discriminated between COVID-positive and COVID-negative individuals yielding receiver operating coefficient curves with an area under curve (AUC) of 0.8 in both males (79% sensitivity and 75% specificity) and females (84% sensitivity and 64% specificity). Taking the sex of the saliva donor into account increased the AUC by 5%. CONCLUSION: These findings may pave the way for new rapid Raman spectroscopic screening tools for COVID-19 and other infectious diseases

Rilpivirine in HIV-1-positive women initiating pregnancy: to switch or not to switch?

International audienceBackgroundSafety data about rilpivirine use during pregnancy remain scarce, and rilpivirine plasma concentrations are reduced during second/third trimesters, with a potential risk of viral breakthroughs. Thus, French guidelines recommend switching to rilpivirine-free combinations (RFCs) during pregnancy.ObjectivesTo describe the characteristics of women initiating pregnancy while on rilpivirine and to compare the outcomes for virologically suppressed subjects continuing rilpivirine until delivery versus switching to an RFC.MethodsIn the ANRS-EPF French Perinatal cohort, we included women on rilpivirine at conception in 2010–18. Pregnancy outcomes were compared between patients continuing versus interrupting rilpivirine. In women with documented viral suppression (<50 copies/mL) before 14 weeks of gestation (WG) while on rilpivirine, we compared the probability of viral rebound (≥50 copies/mL) during pregnancy between subjects continuing rilpivirine versus those switching to RFC.ResultsAmong 247 women included, 88.7% had viral suppression at the beginning of pregnancy. Overall, 184 women (74.5%) switched to an RFC (mostly PI/ritonavir-based regimens) at a median gestational age of 8.0 WG. Plasma HIV-1 RNA nearest delivery was <50 copies/mL in 95.6% of women. Among 69 women with documented viral suppression before 14 WG, the risk of viral rebound was higher when switching to RFCs than when continuing rilpivirine (20.0% versus 0.0%, P = 0.046). Delivery outcomes were similar between groups (overall birth defects, 3.8/100 live births; pregnancy losses, 2.0%; preterm deliveries, 10.6%). No HIV transmission occurred.ConclusionsIn virologically suppressed women initiating pregnancy, continuing rilpivirine was associated with better virological outcome than changing regimen. We did not observe a higher risk of adverse pregnancy outcomes